When a consumer is prescribed with glasses, because each person's pupil distance, head shape, and face shape are different, a trial frame is needed to measure associated information to make the glasses perfectly fit to the consumer.
A professional optometrist is required for using the trial frame, so as to correctly read data of the trial frame. Therefore, if desiring a highly customized frame, the consumer not only has to pay a higher fee, but also has to attend a specific location at which the optometrist is on duty.